Field
This indention relates to flexible cyanoacrylate-containing compositions, having improved torsion stress resistance particularly when bonded to plastic substrates.
Brief Description of Related Technology
Cyanoacrylate adhesive compositions are well known, and widely used as quick setting, instant adhesives with a wide variety of uses. See; H. V. Coover, D. W. Dreifus and J. T. O'Connor, “Cyanoacrylate Adhesives” in Handbook of Adhesives, 27, 463-77, I. Skeist, ed., Van Nostrand Reinhold, New York, 3rd ed. (1990). See also G. H. Millet, “Cyanoacrylate Adhesives” in Structural Adhesives: Chemistry and Technology, S. R. Hartshorn, ed., Plenun Press, New York, p. 249-307 (1986).
Cyanoacrylate compositions ordinarily tend to cure to form relatively brittle polymeric materials. This is an undesirable property for certain applications where a degree of flexibility in the polymeric material is desired. Such applications include bonding flexible materials where a degree of flexibility in the bond to match the flexibility of the material is desired. It is also desirable to have a flexible polymeric material in applications where the polymeric material may be subjected to varying forces in its end-use application. For example if the polymeric material has bonded together two substrates, the substrates may not remain in an undisturbed condition but may be subject to external forces, for example where the substrates, form part of a moving object, or part of a stationary object which is subjected to one or more continuous or occasional forces from other moving objects.
In the past, efforts have been made to improve the flexibility of cured products of cyanoacrylate compositions. See e.g. U.S. Pat. Nos. 2,776,232, 2,784,215, 2,784,127, 3,699,127, 3,961,966, 4,364,876, and 4,444,933.
One approach to overcoming the brittleness of polymerized cyanoacrylate adhesives has been to plasticize the composition through the use of monomer mixtures. The use of mixtures of cyanoacrylate monomers is thought to result in a more flexible polymeric material when the monomer mixture is cured. A second approach has been to incorporate plasticizers into cyanoacrylate compositions. The flexibility here is generally obtained at the expense of cure speed and/or bond strength.
U.S. Pat. No. 6,977,278 describes certain cyanoacrylate compositions comprising: (i) at least one lower cyanoacrylate monomer component selected from ethyl cyanoacrylate and methoxycyanoacrylate; (ii) at least one higher cyanoacrylate monomer component in an amount greater than 12% by weight based on the total weight of the combination, of the lower cyanoacrylate monomer and the higher cyanoacrylate monomer, and selected from n-propyl-cyanoacrylate, iso-propyl cyanoacrylate, n-butylcyanoacruylate, sec-butyl-cyanoacrylate, iso-butyl-cyanoacrylate, tert-butyl-cyanoacrylate, n-pentyl-cyanoacrylate, 1-methyl-butyl-cyanoacrylate, 1-ethyl-propyl-cyanoacrylate, neopentyl-cyanoacrylate, n-hexyl-cyanoacrylate, 1-methyl pentyl-cyanoacrylate, n-heptyl-cyanoacrylate, n-octyl-cyanoacrylate, n-nonyl-cyanoacrylate, n-decyl-cyanoacrylate, n-undecyl-cyanoacrylate, n-dodecyl-cyanoacrylate, cyclohexyl-cyanoacrylate, benzyl-cyanoacrylate, phenyl-cyanoacrylate, tetrahydrofurfuryl-cyanoacrylate, allyl cyanoacrylate, propargyl-cyanoacrylate, S-butenyl-cyanoacrylate, phenethyl-cyanoacrylate, chloropropyl-cyanoacrylate, ethoxyethyl-cyanoacrylate, ethoxypropyl-cyanoacrylate, ethoxy isopropyl-cyanoacrylate, propoxyethyl-cyanoacrylate, isopropoxyethyl-cyanoacrylate, butoxyethyl-cyanoacrylate, methoxypropyl-cyanoaorylate, methoxy isopropyl-cyanoacrylate, methoxy butyl-cyanoacrylate, propoxymethyl-cyanoacrylate, propoxy ethyl-cyanoacrylate, propoxy propyl-cyanoacrylate, butoxymethyl-cyanoacrylate, butoxyethyl-cyanoacrylate, butoxypropyl-cyanoacrylate, butoxyisopropyl-cyanoacrylate, butoxy butyl-cyanoacrylate, iso-nonyl-cyanoacrylate, iso-decyl-cyanoacrylate, cyclohexyl methyl-cyanoacrylate, naphtyl-cyanoacrylate, 2-(2′-methoxy)-ethoxy-ethyl-cyanoacrylate, 2-(2′-ethoxy)-ethoxy ethyl-cyanoacrylate, 2-(2′-propyloxy)-ethoxy ethyl-cyanoacrylate, 2-(2′-butyloxy)-ethoxy ethyl-cyanoacrylate, 2-(2′-pentyloxy)-ethoxy ethyl-cyanoacrylate, 2-(2′-hexyloxy)-ethoxy ethyl-cyanoacrylate, 2-(2-methoxy)-propyloxy propyl-cyanoacrylate, 2-(2′-ethoxy)-propyloxy propyl-cyanoacrylate, 2-(2′-propyloxy)-propyloxy propyl-cyanoacrylate, 2-(2′-pentyloxy)-propyloxy propyl-cyanoacrylate, 2-(2′-hexyloxy)-propyloxy propyl-cyanoacrylate, 2-(2′-methoxy)-butyloxy butylcyanoacrylate, 2-(2′-ethoxy)-butyloxy butyl-cyanoacrylate, 2-(2′-butyloxy)-butyloxy butyl-cyanoacrylate, 2-(3′-methoxy)-propyloxy ethyl-cyanoacrylate, 2-(3′-methoxy)-butyloxy ethyl-cyanoacrylate, 2-(3′-methoxy)-pxopyloxy propyl-cyanoacrylate, 2-(3′-methoxy)-butyloxy propyl-cyanoacrylate, 2-(2′-methoxy)-ethoxy propyl-cyanoacrylate, and 2-(2′-methoxy)-ethoxy, butyl-cyanoacrylate; (iii) at least one plasticizer component comprising at least one ester group containing plasticizer, the plasticizer component being miscible in a mixture of component (i) and component (ii); the plasticizer component being present in the composition in an amount between about 15 to about 40% by weight of the composition, and the plasticizer component having an Ap/Po ratio in the range of about 1 to less than about 6, provided the plasticizer component does not include pentaerythritoltetrabenzoate as the sole plasticizer.
The '273 patent makes clear that amounts of plasticizer up to 12 weight percent do not result in the desired properties and very high amounts of plasticizer deleteriously affect cure speeds and bond strength so that it appears that the desired flexibility can be achieved in the cured compositions if amounts less than about 40 weight percent are used.
Despite these efforts, there has been a long standing, but unmet, desire to achieve a cyanoacrylate showing more robust bond strength while maintaining a degree of flexibility. It would accordingly be quite advantageous to provide a solution to that desire.
The present invention remedies the shortcomings of compromised bond strength when improvements to flexibility in cyanoacrylate compositions has been achieved, by providing cyanoacrylate-containing compositions, having improved torsion stress resistance particularly when bonded to plastic substrates.
More specifically, provided herein are cyanoacrylate-containing compositions having a cyanoacrylate component based on the combination of ethyl-2-cyanoacrylate and octyl-2-cyanoacrylate, together with about 5 weight percent to about 12 weight percent of acetyl triacetyl citrate.
In addition, provided herein is a method of bonding together plastic substrates using cyanoacrylate compositions, which when subjected to torsional strain, show improved performance. Indeed, the performance is so improved that substrate failure is observed rather than either adhesive or cohesive failure of the cured cyanoacrylate composition/substrate interface.
The method involves providing a cyanoacrylate-containing composition having a cyanoacrylate component based on the combination of ethyl-2-cyanoacrylate and octyl-2-cyanoacrylate, together with about 5 weight percent to about 12 weight percent of acetyl triacetyl citrate; providing one or more plastic parts to be bonded together; and applying the cyanoacrylate-containing composition to at least a portion of a surface of the part(s) to be bonded and maintaining the cyanoacrylate-containing composition applied part for a period of time sufficient to form a bond.
In addition, the present invention is directed to reaction products of the inventive compositions.
Also, the invention is directed to a method of preparing the inventive compositions.
The invention will be more fully understood by a reading of the section entitled “Detailed Description”, which follows.